Date post: | 16-Dec-2015 |
Category: |
Documents |
Upload: | noel-palmer |
View: | 216 times |
Download: | 1 times |
LCLS
Linac Coherent Light SourceLinac Coherent Light SourceUpdateUpdate
John N. GalaydaJohn N. GalaydaLCLS Project ManagerLCLS Project Manager
Basic Energy Sciences Advisory Committee MeetingBasic Energy Sciences Advisory Committee Meeting2-3 August 20012-3 August 2001
LCLS
R&D progress•Gun•Bunch compression•Undulator•X-ray optics•FEL experiments
Near-term R&D goals•Determine baseline gun performance•Improve understanding of coherent synchrotron radiation effects•Sub-Picosecond Photon Source (SPPS)
LCLS
1977-1990
National Synchrotron Light Source, Brookhaven National Lab
1990-2001
Advanced Photon Source,
Argonne National Lab
LCLS
LLINACINAC C COHERENTOHERENT L LIGHTIGHT S SOURCEOURCE
I-280I-280
Sand Hill RdSand Hill Rd
LCLS
Peak and time
averaged
brightness
of the LCLS and
other facilities
operating or
under
construction
Performance Characteristics of the LCLS
~ TESLA Performance
LCLS
Electrons are bunched under the influence of the light that they radiate.The bunch dimensions are characteristic of the wavelength of the light.
Excerpted from the TESLA Technical Design Report, released March 2001
Self-Amplified Spontaneous Emission
LCLS
At entrance to the undulator Exponential gain regime Saturation(maximum bunching)
Excerpted from the TESLA Technical Design Report, released March 2001
LCLS
R&D progress – Gun
BNL Accelerator Test Facility•Measurement of 0.8 mm-mrad emittance with 0.5 nC of charge•Such high performance could make shorter LCLS pulses possible•Details to be published in NIM-A, 2001 FEL Conference Proceedings
LCLS
Charge, picocoulombs
mm
-mra
dR&D progress – Gun
SLAC gun test facility•Comparison of computed and measured emittances•Agreement is good for configurations tested thus far•Facility upgrades planned to study configurations with lower emittance
LCLS Specification
LCLS
Producing short bunches
At low energy, space charge repulsion degrades the beam properties
Accelerate the bunch, then compress it.
SLAC linac tunnel undulator hall
Linac-0L6 m
Linac-1L9 mrf 38°
Linac-2L330 mrf 43°
Linac-3L550 mrf 10°
BC-1L6 m
R56 36 mm
BC-2L24 m
R56 22 mm DL-2L66 mR56 = 0
DL-1L12 mR56 0
undulatorL120 m
7 MeVz 0.83 mm 0.2 %
150 MeVz 0.83 mm 0.10 %
250 MeVz 0.19 mm 1.8 %
4.54 GeVz 0.022 mm 0.76 %
14.35 GeVz 0.022 mm 0.02 %
...existing linac
new
RFgun
25-1a30-8c
21-1b21-1d
21-3b24-6dX
Linac-XL0.6 mrf=
LCLS
zz
zz
zz
VV = = VV00sin(sin())
zz00
zz
zz = = RR5656
Under-Under-compressioncompression
Over-Over-compressioncompression
RF AcceleratingRF AcceleratingVoltageVoltage
RF AcceleratingRF AcceleratingVoltageVoltage
Path Length-EnergyPath Length-EnergyDependent BeamlineDependent Beamline
Path Length-EnergyPath Length-EnergyDependent BeamlineDependent Beamline
LCLS
Coherent Synchrotron Radiation (CSR)Coherent Synchrotron Radiation (CSR)Coherent Synchrotron Radiation (CSR)Coherent Synchrotron Radiation (CSR)
RR
e–
Free space radiation from bunch tail at pointFree space radiation from bunch tail at point AA overtakes bunch head, a overtakes bunch head, a distancedistance ss ahead of the source, at the pointahead of the source, at the point BB which satisfies...which satisfies...
ss = arc( = arc(ABAB) – |) – |ABAB| = | = RR – 2 – 2RRsin(sin(/2) /2) RR 3 3/24/24
and forand for ss = = zz (rms bunch length) the overtaking distance is...(rms bunch length) the overtaking distance is...
LL00 | |ABAB| | (24 (24zzRR22))1/31/3, (, ( LCLSLCLS: : LL00 ~ 1 m ~ 1 m))
Free space radiation from bunch tail at pointFree space radiation from bunch tail at point AA overtakes bunch head, a overtakes bunch head, a distancedistance ss ahead of the source, at the pointahead of the source, at the point BB which satisfies...which satisfies...
ss = arc( = arc(ABAB) – |) – |ABAB| = | = RR – 2 – 2RRsin(sin(/2) /2) RR 3 3/24/24
and forand for ss = = zz (rms bunch length) the overtaking distance is...(rms bunch length) the overtaking distance is...
LL00 | |ABAB| | (24 (24zzRR22))1/31/3, (, ( LCLSLCLS: : LL00 ~ 1 m ~ 1 m))
Coherent Coherent radiation for:radiation for:rrzz
Coherent Coherent radiation for:radiation for:rrzz
rr
zz
...from Derbenev, et. al....from Derbenev, et. al.
LCLS
CSR Effects CSR Effects Bunch Energy Gradient Bunch Energy GradientCSR Effects CSR Effects Bunch Energy Gradient Bunch Energy Gradient
zz
Charge distributionCharge distribution
~CSR wakefield~CSR wakefield
HEADHEAD
TAILTAIL
(mean loss)(mean loss)
2 3 4 30.22 e Brms
z
r NLE E
R 2 3 4 30.22 e B
rmsz
r NLE E
R
zz
LCLS
CSR Effects CSR Effects Emittance Growth Emittance GrowthCSR Effects CSR Effects Emittance Growth Emittance Growth
s
Radiation in bendsRadiation in bendsRadiation in bendsRadiation in bendsEnergy loss in bends causesEnergy loss in bends causestransverse position spread aftertransverse position spread afterbends bends xx-emittance growth-emittance growth
Energy loss in bends causesEnergy loss in bends causestransverse position spread aftertransverse position spread afterbends bends xx-emittance growth-emittance growth
LCLS
R&D Progress – Coherent Synchrotron Radiation•CSR sets a lower limit on LCLS as a laser•LCLS could produce ~50 fsec pulses of spontaneous radiation•New ANL model fits latest data – is the model accurate?•LCLS bunch compression can be retuned to accommodate
ener
gyen
ergy
spre
ad
spre
ad
[%]
[%]
rms
rms
bun
ch
bun
ch
leng
th
leng
th
[ps
[ps ]]
emitt
ance
em
ittan
ce
[mm
-mra
d][m
m-m
rad]
minimum compressionminimum compression
ElegantElegantmodelmodel
Courtesy M. Borland, J. Lewellen, Courtesy M. Borland, J. Lewellen, ANLANLCourtesy M. Borland, J. Lewellen, Courtesy M. Borland, J. Lewellen, ANLANL
QQ 0.3 nC 0.3 nCM. Borland, PRST-AB v.4, 074201(2001)Borland, Braun, Doebert, Groening, & Kabel, CERN/PS 2001-027(AE)
LCLS
R&D Progress – Prototype Undulator
•Titanium strongback mounted in eccentric cam movers
•Magnet material 100% delivered
•Poles >90% delivered
•Assembly underway
LCLS
Helmholtz Coil – magnet block measurement Translation stages for undulator segment
Poletip alignment fixture Magnet block clamping fixtures
LCLS
Planned beam diagnostics in undulator include pop-in C(111) screenTo extract and observe x-ray beam, and its superposition on e-beam
LCLS
R&D Progress – Undulator diagnostics•P. Krejcik, W. K. Lee, E. Gluskin•Exposure of diamond wafer to electron beam in FFTB-•Same electric fields as in LCLS•No mechanical damage to diamond•Tests of crystal structure planned
Before After
LCLS
R&D Progress – X-ray optics
•LLNL tests of damage to silicon crystal•Exposure to high- power laser with similar energy deposition•Threshold for melting 0.16 J/cm2, as predicted in model
•Fabrication/test of refractive Fresnel lens•Made of aluminum instead of carbon•Machined with a diamond point•Measurements from SPEAR presently under analysis
LCLS
FocusingOptic
Incident BeamMonitors
Back-scatterx-ray
spectrometer
Spectrometer
Laser
Outgoing Beam
Monitor
FELBeam
100 mm thick
sample50-100 maperture
Variablebeam
attenuator
250 maperture
Imagingdetector
OpticsTank
SampleTank
WDM Shielded Room
PPS beam stops
13 m
Warm Dense Matter Experiment
LCLS
R&D Progress – FEL physics
•More complete analysis of HGHG•A. Doyuran, et al. PRL vol. 86, Issue 26, pp. 5902-5905, June 25, 2001
•LEUTL experiments ongoing•Milton, et al. Science vol. 292, Issue 5524, 2037-2041, June 15, 2001
•VISA experiment saturation•To be published in proceedings of 2001 FEL conference
Data from BNL/ANLHigh-Gain HarmonicGeneration(HGHG)Experiment
LCLS
Distance Traversed in Undulator (m)
Rad
iate
d E
ner
gy
(a.u
.)LEUTL Gain Curve @ 530 nm on March 10, 2001
107
106
105
104
103
102
101
100
0 5 10 15 20 25
October,2000
LCLS
Preliminary recent results (unpublished) from VISA showing large gain (2 106) in SASE FEL radiation and evidence of saturation at 830 nm.
Visible to Infrared SASE Amplifier
Enclosure for 4-m long VISA undulator
Enclosure for 4-m long VISA undulator
Pop-In DiagnosticsPop-In Diagnostics
Data Points taken along VISA Undulator
Data Points taken along VISA Undulator
Direction of Electron Beam
Direction of Electron Beam
Wavelength 830 nm
Wavelength 830 nm
Onset of Saturation
Onset of Saturation
VISA Pulse Energy vs. Position
Wavelength 830nmRMS Bunch Length: 900 fsAverage Charge: 170 pCPeak Current: ~200 AMeasured Projected Emittance: 1.7 mm mradEnergy Spread: 7×10-4
Gain Length 18.5 cmEquivalent Spontaneous Energy: 5 pJPeak SASE Energy: 10 JTotal Gain: 2×106
16 March 2001
BNL-LLNL-SLAC-UCLA
LCLS
Near-term R&D goals
•Gun R&D•Thorough investigation of gun operation at LCLS parameters
•Laser upgrade•Linac energy upgrade
•Experiment/model comparison at 1 mm-mrad emittance, 0.5-1 nC
•Bunch compression, coherent synchrotron radiation•Install a bunch compressor in the SLAC linac•Continue start-to-end modeling
LCLS
Bunch compression studies with SLAC linac in 2003
•Compatible with PEP-II injection•Capable of producing 80 fsec electron bunches
• Goal: first studies in 1/2003, 1 year of tests•pump/probe techniques•Accelerator physics opportunities to study wake fields
Of great importance to LCLS
Short bunches are ideal for advanced accelerator R&D; Strong SLAC support
LCLS
LCLS – X-ray Laser Physics The “sixth” experiment – Produce < 230 fsec pulses of SASE radiation
LCLS will be used to explore means of producing ultra short bunches (< 50 fs). Alternative techniques will be investigated:
Stronger compression of the electron bunch• No new hardware is required
Photon bunch compression or slicing• Principle: spread the electron and photon pulses in energy;
recombine optically or select a slice in frequency
z
Seeding the FEL with a slice of the photon pulse
•Principle: select slice in frequency, then use it to seed the FEL
LCLS
Two-Stage Chirped-Beam SASE-FEL for High Power Femtosecond X-Ray Pulse GenerationC. Schroeder*, J. Arthur^, P. Emma^, S. Reiche*, and C. Pellegrini*
^ Stanford Linear Accelerator Center*UCLA
Strong possibility for shorter-pulse operation
LCLS
Two-stage Two-stage undulator for undulator for shorter pulseshorter pulse
52 m52 m43 m43 m
ee
30 m30 m
SASE gain (SASE gain (PPsatsat/10/1033)) SASE Saturation (23 GW)SASE Saturation (23 GW)
SiSi monochromator monochromator((TT = 40%) = 40%)
timetime
Ene
rgy
Ene
rgy
timetime
Ene
rgy
Ene
rgy
EEFWFW//EE = 1.0% = 1.0%
timetime
ttFWFW = 230 fsec = 230 fsec
x-ray pulsex-ray pulse
1.01.0101044
timetime
ttFWFW < 10 fsec < 10 fsecMitigates Mitigates ee energy energy jitter and jitter and undulator undulator wakeswakes
Mitigates Mitigates ee energy energy jitter and jitter and undulator undulator wakeswakes
Also a Also a DESYDESY scheme which emphasizes line-width reduction (B. Faatz) scheme which emphasizes line-width reduction (B. Faatz)
UCLUCLAA
LCLS
LCLS Construction
•FY2003: $6M for project engineering and design, $3M for R&D•Prepare bid packages
•FY2004: Start of Construction•Injector construction and installation•Bunch compressor construction•Start construction of near hall•Undulator procurement
•FY2005:•Injector commissioning•Bunch compressor installation•Start construction of far hall•Undulator, experiment construction
•FY2006: Installation•Linac commissioning•Undulator and experiment installation•LCLS commissioning
LCLS
LCLS research activities span the full range of challenges to be met in creating and exploiting an x-ray laser
SLAC has supplemented its extraordinary capabilities with the expertise and resources at partner labs to make LCLS possible
LCLS can be a reality by 2007
LCLS
End of Presentation